I think it's better to split this one up.
First, rank their NC (or nearly NC) teams: 1982, 1986 and 1994.
Then the more fun part, the best non-NC teams:
1947: Finished 9-0-1, with the tie coming against #13 SMU in the Cotton Bowl. Outscored their opponents 319-25, with 6 shutouts in 9 games. Didn't exactly play a gauntlet of a schedule. That Cotton Bowl was their only game against a ranked team. Finished #5 in the polls.
1968: Finished 11-0, and ranked #2. Again victimized by a weak schedule that saw them face no ranked teams until a 15-14 win over #6 Kansas in the Orange Bowl. They were led by TE Ted Kawlick, PSU's first two time All-American.
1969: Again 11-0, again #2. They at least faced one ranked team this time, beating West Virginia. They fell to #8 after narrowly beating a bad Syracuse team, and never recovered. This was also when Richard Nixon attended the Texas-Arkansas game, and declared the winner to be national champion before the game. Paterno famously later wondered how Nixon knew so little about Watergate, but so much about college football. Season finished with a win over #6 Missouri in the Orange Bowl. The best player was DT Mike Reid, who won the Outland and Maxwell Awards. Oddly, he was an accomplished musician who played piano for several symphony orchestras, including Dallas and Cincinnati. He abruptly retired from the NFL after 4 seasons, inlcuding back to back All-Pro years, to focus on music. He's had a #1 hit and a Grammy as a country music writer.
1971: Led by two headed rushing attack of Franco Harris and John Cappelletti, PSU rolled over 10 straight opponents, and only Air Force (16-14) stayed within 28 points of them. Same thing though, weak schedule. First ranked opponent was a loss at #12 Tennessee by 20 in the season finale. Turned around and thumped Texas by 24 in the Cotton Bowl.
1973: Finished 11-0, with a 35-13 win over #20 Pitt, and 16-9 over #13 LSU in the Orange Bowl. John Cappelletti won the school's first Heisman. Finished ranked #5.
1977: Finished 11-1 and ranked #5. An early season upset loss to Kentucky derailed their NC hopes, but a season finale win over Pitt, with both ranked in the top 10 is legendary. Second half was notable for the snow falling in Pittsburgh, and PSU won by stuffing Pitt on a 2 point conversion, after Pitt scored a TD with 12 second left. The win over #15 Arizona State (along with Nebraska playing 2 years earlier) is what began to cement the Fiesta Bowl's legitimacy.
1978: Beat #6 Ohio State (19-0), #5 Maryland (27-3) and #15 Pitt (17-10) to reach #1 in the polls going into the bowl games, where they lost to #2 Alabama in the Sugar Bowl 14-7 in the de facto national championship game. Chuck Fusina won the Maxwell Award (#2 in the Heisman) and 3 OL were drafted in the 1979 NFL Draft.
1981: Finished #3 in the polls after being ranked #1 until a Halloween upset loss to Miami that cemented the start of the Canes' rise to the top. After another loss to #6 Alabama to fall to #13, Penn State recovered to beat Notre Dame, and then upset rival, and #1, Pitt, to ruin their national title hopes. Finished with a win over #8 USC in the Fiesta Bowl.
1991: Finished 11-2 and ranked #3. Played a schedule that saw them face four top 12 teams, and win 3 of them, the lone loss being a 26-20 loss at eventual national champion Miami. They beat #8 Georgia Tech, #12 Notre Dame and #10 Tennessee by an average of 20 points. They also held BYU to their lowest offensive output in 5 years, sacking defending Heisman Trophy winner Ty Detmer 6 times.
2005: Finished 11-1 and ranked #3, with the lone blemish being in Ann Arbor on Mario Manningham's catch on the final play of the game. Probably wouldn't have mattered as even an undefeated PSU would have been #3 behind USC and Texas that year. Coming off back to back losing seasons, Penn State wasn't even ranked until a 44-14 win over #18 Minnesota, shot them up to #16 in the October 2 poll, and a big night game win that made the Happy Valley White Out a thing occurred the following week against #6 Ohio State. Closed with a triple OT win over #22 Florida State in the Orange Bowl. LB Paul Posluszny won the Bednarik and Butkus Awards, while QB Michael Robinson won the Silver Football.
2016: After September losses to Pitt and Michigan left PSU 2-2 and unranked, James Franklin's time seemed numbered. They then won 9 consecutive games, including over #2 Ohio State and #6 Wisconsin, to win the Big Ten title and play #9 USC in the Orange Bowl, losing by 3. Penn State didn't crack the polls until October 23, reaching as high as #5 following their Big Ten Championship Game win. RB Saquon Barkley won the Silver Football.
2017: Preseason #6, got as high as #2, which they cemented with a 42-13 win over #19 Michigan. Back to back losses by a combined 4 points to #6 Ohio State and #24 Michigan State ended their Big Ten title hopes. They finished on a 4 game winning streak, including a win over #12 Washington in the Fiesta Bowl, their first major bowl win in 12 years.